Drilling fluid



United States Patent 3,492,227 DRILLING FLUID Jack H. Kolaian, Houston, Tex., assiguor to Texaco Inc., New York, N.Y., a corporation of Delaware N0 Drawing. Filed Apr. 25, 1967, Ser. No. 633,402 Int. Cl. Cltlm 3/26, 3/04 US. Cl. 252-85 6 Claims ABSTRACT OF THE DISCLOSURE An aqueous drilling fluid dispersant and a method of drilling wells using said drilling fluid which contains as the dispersant 2,4-dinitro-1,3-dihydroxybnzene.

This invention relates to a novel aqueous drilling fluid for drilling wells through sub-surface formations by means of well drilling tools, and particularly to such an aqueous well drilling fluid having improved dispersibility as a result of containing therein a novel dispersant as hereinafter more fully described. The invention is. also concerned with a method of drilling wells employing the novel aque- Ous drilling fluid.

Drilling fluids, or muds as they are sometimes called, are slurries of clayey solids used in the drilling of wells for tapping underground collections of oil, gas, brine or water. Such fluids have a number of different functions, the most important of which are to assist in the removal of cuttings from the well, to seal off formations of gas, oil or water which may be encountered at different levels, to lubricate the drilling tool and drill pipe which carries the tool, and to hold the cuttings in suspension in event of shut-downs in drilling.

An ideal drilling fluid is a thixotropic colloidal system, i.e., a fluid which on agitation or circulation (as by pumping or otherwise), has a measurable relatively low viscosity and is free flowing (not plastic), particularly at high temperatures; but when such agitation or circulation is halted, the fluid sets or gels. The rate of gel formation is such as to permit the cuttings to fall only a short distance before the gel structure is sufliciently strong to support them.

When such a drilling fluid having the proper viscosity, the proper gel rate and proper gel strength is circulated through a well bore, it has a sufli-ciently high viscosity to carry the cuttings and sand from the bottom of the hole to the surface and it has a gel rate such as to allow the cuttings and sand to settle in a settling pit. On standing in a quiescent state, it develops suflicient gel strength to prevent the settling of the cuttings, sand or weighting material, etc., in the well bore when it becomes necessary to discontinue circulation for any appreciable period of time. Such a fluid is also characterized by its ability to form a mud cake on the borehole wall, thereby assisting in sealing off the traversed formations and inhibiting socalled water loss, i.e., loss of water from the drilling fluid.

One of the principal problems in mud chemistry is the production of suitable drilling fluids having satisfactory dispersibility, and the necessary thixotropic properties dis cussed above.

3,492,227 Patented Jan. 27, 1970 ice In accordance with the present invention the problems of dispersibility in aqueous drilling fluids can be solved by incorporating in an aqueous drilling fluid as the dispersant 2,4-dinitro-1,3-dihydroxybenzene in an amount sufficient to reduce the viscosity thereof.

It is surprising that this compound is an effective drilling fluid dispersant when I-hydroxy-Z,4-dinitronaphthalene is an ineffective drilling fluid dispersant.

It is known from the article appearing in Zhur. Priklad. Khem. 35, pages 638647 (1962), Organic Viscosity Reducer in Clay Solutions by D. Tischenko and S. Fleisher (CA, 57, 2491g, 1962), that the ortho-dihydroxybenzenesulfonic acids, the ortho-dihydroxy-alpha-toluenesulfonic acids and water soluble salts thereof are viscosity reducing agents in clay laden drilling fluids whereas the corresponding metaand para-dihydroxybenzenes including the corresponding sulfonic acid derivatives and water soluble salts thereof are ineffective viscosity reducing agents for aqueous drilling fluids.

The 2,4-dinitro-1,3-dihydroxybenzene of the present invention may be added to an aqueous drilling fluid in amounts ranging from about 0.1 pound to about 10 pounds per barrel of drilling fluid. In general, it has been found that amounts less than 0.1 pound per barrel do not produce completely satisfactory results in terms of dispersing activity whereas amounts above about 10 pounds per barrel are economically unattractive and no improved results are obtained therewith. A preferred range for the 2,4-dinitro-l,3-dihydroxybenzene of the present invention is from about 0.25 to about 5 pounds per barrel of drilling fluid for most consistent results and efliciency.

The 2,4-dinitro-1,3-dihydroxybenzene employed in the present invention is a known compound and the manner of its preparation is known in the art.

In the table, gel strength (gels) is reported as determined by a shearometer in accordance with the procedure in the American Petroleum Institute publication RP-29, results being expressed either as pounds/ square feet or as time in seconds for a tube to settle in the mud (after the mud has stood for zero time and for 10 minutes). If it settles in more than 60 seconds, shear is reported as pounds per hundred square feet. Yield point (YP) is calculated by subtracting the plastic viscosity (PV) from the Fann viscosity reading at 300 rpm. Plastic viscosity (PV) is obtained by calculation, subtracting the Penn reading at 300 r.p.m. from the 600 rpm. reading. Apparent viscosity (AV) is equal to one half of the Faun viscosity reading obtained at 600 rpm. The fluidity of a mud can be back calculated from these data, the results being expressed in Fann viscosity at 600 r.p.m. and 300 rpm. for a direct reading viscosimeter.

The properties of the base mud are shown in the table.

The test data set forth in the following table indicates the surprising advantages resulting by the use of 2,4-dinitro-1,3-dihydroxybenzene as the dispersant in the drilling fluid of the present invention and demonstrate the beneficial results of same in improving the dispersibility of drilling fluids.

Representative physical properties of drilling fluids both before and after addition of various materials including the 2,4-dinitro-1,3-dihydroxybenzene of the pres- 4 which comprises contacting said earth formations with an aqueous drilling fluid containing clayey solids and at least 0.1 pound per barrel of drilling fluid of 2,4-dinitro-l,3- dihydroxybenzene, said dihydroxybenzene being present in cut invention are shown in the table. In each example the amount of material or materials added to the base muds, if any, are shown, expressed in terms of pounds of material per barrel of drilling fluid.

TABLE Shearometer Amount Ap. 1b./10D it. AP! and Type Vis., W.L., Time, Ex. Type Mud Dlspersant PV YP ope. 0 pH cc. hrs.

1 53 g 53 o 3.1 9.4 16.6{ 5 1a 20A ll 5 13.5 2 1 L1. l a .2 ml p I 2 0 B 3 3L5 11 9.6 14.2 16 a 7 5 24.5 2 18 28 8.5 19 9.6 15.2{ 16 LpH=Low pH Mud. A.=2,4-dinitr0-1,3-dihydroxybenzene. d B l-hydroxy-2,4-dlnitronaphthalene:

the drilling fluid in an amount sutncient to impart a reduced viscosity thereto.

5. In a method of drilling wells as claimed in claim 4 wherein 2,4-dinitro-1,3-dihydroxybenzene is present in the drilling fluid in an amount of from 0.1 to 10 pounds per barrel of drilling fluid;

6. In a method of drilling wells as claimed in claim 5 wherein 2,4-dinitro-1,S-dihydroxybenzene is present in the drilling fluid in an amount of from 0.25 to 5 pounds per barrel of drilling fluid.

References Cited UNITED STATES PATENTS an amount sufiicient to impart a reduced viscosity thereto. 1 999 766 4/1935 Lawton et a1 5 Z. An aqueous drilling fluid as claimed in claim 1 3:1 9:59 /19 5 Brink E32 8 5 wherein 2,4-dinitro-1,3-dihydroxybenzene is present in the 3,293,177 12/1966 Stratum 252 3-5 drilling fluid in an amount of from 0.1 to 10 pounds per barrel of drilling fluid. OTHER REFERENCES 3. An aqueous drilling fluid as claimed in claim 2 wherein 2,4-dinitro-1,3-dihydroxybenzene is present in the drilling fluid in an amount of from 0.25 to 5 pounds per barrel of drilling fluid.

4. In a method of drilling wells wherein a drilling fluid is passed through the well in contact with earth formations, during the drilling operation, the improvement Tishchenko et a1., organic viscosity depressants for drilling fluids, article in Journal of Applied Chemistry of the U.S.S.R., vol. 35, No. 3, March 1962, pages 611 to 619.

HERBERT B. GUYNN, Primary Examiner US. Cl. X.R. 252-351 

